(function ($, window, document, undefined) {
    var OnePageNav = function (elem, options) {
        this.elem = elem;
        this.$elem = $(elem);
        this.options = options;
        this.metadata = this.$elem.data("plugin-options");
        this.$win = $(window);
        this.sections = {};
        this.didScroll = false;
        this.$doc = $(document);
        this.docHeight = this.$doc.height()
    };
    OnePageNav.prototype = {
        defaults: {
            navItems: "a",
            currentClass: "current",
            changeHash: false,
            easing: "swing",
            filter: "",
            scrollSpeed: 750,
            scrollThreshold: 0.5,
            space: 0,
            begin: false,
            end: false,
            scrollChange: false
        },
        init: function () {
            this.config = $.extend({}, this.defaults, this.options, this.metadata);
            this.$nav = this.$elem.find(this.config.navItems);
            if (this.config.filter !== "") {
                this.$nav = this.$nav.filter(this.config.filter)
            }
            this.$nav.on("click.onePageNav", $.proxy(this.handleClick, this));
            this.getPositions();
            this.bindInterval();
            this.$win.on("resize.onePageNav", $.proxy(this.getPositions, this));
            return this
        },
        adjustNav: function (self, $parent) {
            self.$elem.find("." + self.config.currentClass).removeClass(self.config.currentClass);
            $parent.addClass(self.config.currentClass)
        },
        bindInterval: function () {
            var self = this;
            var docHeight;
            self.$win.on("scroll.onePageNav", function () {
                self.didScroll = true
            });
            self.t = setInterval(function () {
                docHeight = self.$doc.height();
                if (self.didScroll) {
                    self.didScroll = false;
                    self.scrollChange()
                }
                if (docHeight !== self.docHeight) {
                    self.docHeight = docHeight;
                    self.getPositions()
                }
            }, 250)
        },
        getHash: function ($link) {
            return $link.attr("href").split("#")[1]
        },
        getPositions: function () {
            var self = this;
            var linkHref;
            var topPos;
            var $target;
            self.$nav.each(function () {
                linkHref = self.getHash($(this));
                $target = $("#" + linkHref);
                if ($target.length) {
                    topPos = $target.offset().top;
                    self.sections[linkHref] = Math.round(topPos)
                }
            })
        },
        getSection: function (windowPos) {
            var returnValue = null;
            var windowHeight = Math.round(this.$win.height() * this.config.scrollThreshold);
            for (var section in this.sections) {
                if ((this.sections[section] - windowHeight) < windowPos) {
                    returnValue = section
                }
            }
            return returnValue
        },
        handleClick: function (e) {
            var self = this;
            var $link = $(e.currentTarget);
            var $parent = $link.parent();
            var newLoc = "#" + self.getHash($link);
                if (self.config.begin) {
                    self.config.begin()
                }
                self.adjustNav(self, $parent);
                self.unbindInterval();
                self.scrollTo(newLoc, function () {
                    if (self.config.changeHash) {
                        window.location.hash = newLoc
                    }
                    self.bindInterval();
                    if (self.config.end) {
                        self.config.end()
                    }
                })
            e.preventDefault()
        },
        scrollChange: function () {
            var windowTop = this.$win.scrollTop();
            var position = this.getSection(windowTop);
            var $parent;
            if (position !== null) {
                $parent = this.$elem.find('a[href$="#' + position + '"]').parent();
                if (!$parent.hasClass(this.config.currentClass)) {
                    this.adjustNav(this, $parent);
                    if (this.config.scrollChange) {
                        this.config.scrollChange($parent)
                    }
                }
            }
        },
        scrollTo: function (target, callback) {
            var offset = parseInt($(target).offset().top);
            $("html, body").animate({
                scrollTop: offset - this.config.space
            }, this.config.scrollSpeed, this.config.easing, callback)
        },
        unbindInterval: function () {
            clearInterval(this.t);
            this.$win.unbind("scroll.onePageNav")
        }
    };
    OnePageNav.defaults = OnePageNav.prototype.defaults;
    $.fn.onePageNav = function (options) {
        return this.each(function () {
            new OnePageNav(this, options).init()
        })
    }
})(jQuery, window, document);
